Q: I heard the Illinois Air Team was going to be opening more vehicle emissions test stations throughout the area. Do you know if there is one in or near Tinley Park?--D.A., Tinley Park

A: D.A., yes, there is a test facility in Tinley Park. The address is 7460 Duvan Drive. It's near 175th St. and Harlem Ave. Locate test facilities, visit www.epa.state.il.us/air/vim/ and click on "Test Station Locations."

Q: The brake pedal in my '94 Chevrolet Caprice sometimes doesn't come all the way back after releasing it. This causes my brakes to drag and slow the car down until I reach my foot behind the pedal and force it back all the way. A friend said that it might be a faulty master cylinder or damaged vacuum check valve in the brake booster. What do you think? -- O.B., Chicago

A: O.B., I don't agree with your friend. If the master cylinder pistons were sticking, that would cause the brakes to drag, but it would not cause the brake pedal to sometimes not return all the way. That's because your brake pedal is not directly connected to the master cylinder. There's a brake booster mounted in between the pedal and master cylinder. As for the vacuum check valve in the brake booster, it merely traps enough vacuum in the booster for two or three power-assisted brake applications in case the engine stalls and you need to stop the vehicle. If the vacuum check valve went bad, you'd loose your reserve assisted applications or have a vacuum leak. If the latter was true, the brake booster wouldn't be able to provide as much assist and the brake pedal would be difficult to depress. As long as there's nothing up under your dashboard keeping the brake pedal from returning, and the brake pedal pivot assembly is not binding, I think that the brake booster's internal valves are sticking or its internal return spring is weak. If that's the case, the booster will need to be replaced as it's not serviceable.

Q: Is there an easy way to determine if the head gasket is bad and leaking coolant into the combustion chamber? I have a '96 Ford Escort with a 1.9-liter engine and the repair shop said that my engine is overheating because of a blown head gasket. What else could make the engine overheat? -- S.R., Bridgeview

A: S.R., one of the easiest ways to see if the cylinder head or head gasket is leaking coolant into the combustion chamber is to remove all the spark plugs and look at the electrodes. The spark plug electrodes will be clean in the cylinder or cylinders with a coolant leak. Also, with the spark plugs removed, a pressure tester can be fitted in place of the radiator cap and you can look for the pressure of coolant in the cylinders. A small high-powered flashlight or even a borescope comes in handy. Another method of determining if the head or head gasket is faulty involves using a special piece of equipment (costs around $70) known as a combustion leak detector. It looks like a two-level turkey baster and utilizes a special test fluid. This tester is used to draw air from the cooling system at the radiator with the engine running. If there are combustion gases (carbon-dioxide) present, the test fluid changes color to indicate a potentially damaged cylinder head or head gasket.

AutoAdviser: Ira Siegel is an Automotive Instructor and ASE Certified Master Auto Technician. If you have auto-related questions for Ira Siegel you can call and leave your questions at the Auto Adviser Hotline at 708-633-6839 or e-mail a question to Autoadvisr@aol.com.